You can use the app < group >.
Create a new Contact Sensor device and add the door sensors of the bed- and bathroom.
Move the new < group > device into the living room zone. The default setting of the new device is that the zone activity is switched on, so there is no need to change anything. So if you open the bathroom and/or bedroom door, the living room zone will also be activated.
I hope I have understood your requirements correctly.
